Compound crank mechanism and a conveyor/stacker assembly incorporating said mechanism

ABSTRACT

A compound crank mechanism is disclosed in which rotary motion is used to drive a first crank at the end of which a second crank is journalled. The second crank is constrained to follow a particular hypocycloidal path such that the end of the second crank moves in a substantially linear reciprocal path. Also disclosed is a reciprocating conveyor/stacker assembly incorporating such a crank mechanism.

United States Patent [191 Burton et al.

[ COMPOUND CRANK MECHANISM AND A CONVEYOR/STACKER ASSEMBLY INCORPORATING SAID MECHANISM [75] Inventors: John A. Burton; George H. Eaton,

both of Vancouver, British Columbia, Canada [73] Assignee: Moore Dry Kiln Company of Canada Limited, Richmond, British Columbia, Canada [22] Filed: June 19, 1972 [21] Appl. No.: 263,978

[52] U.S. Cl. 74/52 [51] Int. Cl. Fl6h 37/12 [58] Field of Search 74/52 [56] References Cited UNITED STATES PATENTS 634,194 10/1899 Woodward ..74/52 Apr. 23, 1974 2,628,024 2/1953 Greenwood, Jr. 74/52 3,127,777 4/1964 Pietsch 74/52 2,787,001 4/1957 Stillwell 74/52 Primary Examiner-Benjamin W. Wyche Assistant Examiner-Wesley S. Ratliff, Jr. Attorney, Agent, or FirmFetherstonhaugh & Co.

[ 5 7] ABSTRACT A compound crank mechanism is disclosed in which rotary motion is used to drive a first crank at the end of which a second crank is journalled. The second crank is constrained to follow a particular hypocycloidal path such that the end of the second crank moves in a substantially linear reciprocal pathQAlso disclosed is a reciprocating conveyor/stacker assembly incorporating such a crank mechanism.

5 Claims, 8 Drawing Figures PATENTEDAPR 23 I974 SHEET 1 [IF 2 COMPOUND CRANK MECHANISM AND A CONVEYOR/STACKER ASSEMBLY INCORPORATING SAID MECHANISM The invention relates to compound crank mechanisms and to conveyor/stacker assemblies incorporating such mechanisms.

The use of a crank shaft for conversion of rotary to linear motion is well known. However, the conventional crank shaft can only be used in locations where the linear stroke to be developed does not exceed the transverse space available for rotation of the crank. It is among the objects of the present invention to provide a compound crank mechanism, particularly for use in confined spaces, whereby the abovementioned disadvantage is overcome.

The invention therefore provides a mechanism for converting rotary motion into reciprocating motion, comprising support means, a first element journalled in said support means for rotation about a primary axis, a second element journalled on said first element for rotation about a secondary axis at a position spaced from said primary axis, said second element including a portion spaced from the secondary axis by a distance approximately equal to the spacing between the primary and secondary axes, and means mounted on said support means and operatively connected to said second element for causing said second element to perform a single revolution in one direction about the secondary axis during each single revolution of the first element in the opposite direction about the primary axis, whereby rotation of said first element about said primary axis causes said spaced portion of said second element to perform an approximately reciprocal motion at right angles to said primary axis.

Various embodiments of the invention will now be described with reference to the accompanying drawings in which, I

FIG. 1 is a diagram illustrating the geometry upon which the crank mechanism of the invention is founded,

FIGS. 2'to 4 show three alternative embodiments of crank mechanism according to the invention,

FIG. 5 is a side elevation, partly in section, ofa con veyor assembly according to the invention,

FIG. 6 is a section on the line 6-6 of FIG. 5,

FIG. 7 is an enlarged view of the crank mechanism incorporated in the conveyor assembly of FIG. 5, and

FIG. 8 is a sequence of four views showing the crank mechanism of FIG. 7 in various stages of operation.

The crank mechanism of the invention is founded upon geometry of a particular form of hypocycloid-the curve traced by a point on the circumference of a lesser circle when rolled internally around the circumference of a greater circle. If, as shown in FIG. 1, the lesser circle C, is precisely half the diameter of the greater circle C then a point P on the circumference will trace a line P,-P defining a diameter of the greater circle. In its optimum form, the invention utilizes the linear reciprocating motion of the point P resulting from the rolling movement of the smaller circle Cl.

However, points such as Q and R lying close to andlies sufficiently close to the circumference of the circle C the minor axis Q; or R will be relatively small and such deviation from a linear path is frequently acceptable. It will be ssen that the length of stroke of a device constructed on the above discussed principles can be varied by selecting an appropriate point along the pro jected radius S of the circle C, for derivation of linear motion.

Referring now to FIG. 2, the compound crank mechanism there shown comprises a primary crank I mounted at one end for rotation on a shaft 2, and a secondary crank 3 journalled at one end on the crank pin 4 of the primary crank 1. Also journalled on the crank pin 4 for rotation with the secondary crank 3 is a pinion 5. The shaft 2 is journalled for rotation in a support frame (not shown). An internal ring gear 6 is also mounted fixedly on the support frame coaxially with the shaft 2 for meshing engagement with the pinion 5. The internal ring gear 6 has a pitch circle diameter twice that of the pinion 5.

The length of the secondary crank 3 is somewhat greater than the radius of the pinion 5 so that the end 7 of the secondary crank follows an elliptical path simi-' lar to the path R, of FIG. 1. It will be seen that a substantially linear reciprocal motion can be derived in a connecting rod connected to the end 7 during rotation of the primary crank 1. The motion would be precisely linear if the length of the secondary crank 3 were to be the same as the radius of the pinion 5.

The compound crank mechanism of FIG. 3 comprises a primary crank 11 mounted for rotation on a shaft 12 journalled in a support frame (not shown). A secondary crank 13 has one end journalled for rotation on the crank pin 14 of the primary crank 11. A pinion 15 is also journalled on the crank pin 14 for rotation with the secondary crank 13. An external ring gear 16 is also mounted on the support frame in coaxial relation to the shaft 12. An idler pinion 17 is journalled on a bearing l8on the primary crank 11 and meshes with both the external ring gear 16 and the pinion 15. The pitch circle diameter of the pinion 15 is twice that of the ring gear 16 so that the pinion l5 performs a single revolution in one direction about the crank pin 14 during each revolution of the primary crank 11 in the opposite direction. Linear, or approximately linear motion is derived from the crank mechanism of FIG. 3 by connecting a linkage to the secondary crank 13 at or near the point thereon which follows a hypocyclic path as described above with reference to FIG. 1.

FIG. 4 shows a further embodiment of the invention comprising a primary crank 21 mounted at one end on a main shaft 22 journalled in a support frame (not shown). One end of a secondary crank 23 is journalled on the crank pin 24 of the primary crank. A sprocket wheel 25 is also journalled on the crank pin 24 for rotation with the secondary crank 23. A sprocket wheel 26, having twice the diameter of the sprocket wheel 25 is fixedly mounted in the support frame in coaxial relation to the mainshaft 22. A sprocket chain 27 extends around the sprocket wheels 25 and 26 so that upon each rotation of the primary crank 21 in one direction, the sprocket wheel 25 and secondary crank 23 perform a single revolution in the opposite direction. Linear or approximately linear motion is derived from the crank mechanism of FIG. 4 in the same manner as that of FIG. 3 by connecting a linkage to the secondary crank 3 23 at or near the point thereon which follows a hypocyclic path.

' It will be appreciated that the sprocket wheels and chain could be replaced by other non slip elements such as castellated wheels engaging with a toothed belt, whilst remaining within the ambit of the invention.

FIGS. 5 to 8 show a conveyor assembly incorporating a compound crank mechanism of the kind shown in FIG. 4.

Referring first to FIGS. 5 and 6, the conveyor assembly comprises a support frame 28 having chain wheels 29 mounted for rotation at opposite ends of the frame. Four sets of chain wheels 29 are provided (one set only being shown in FIG. 6), each set having an endless chain 30 extending therearound. Adjacent to each chain 30, a stacker arm 33 is provided in parallel relation to the chain (see also FIG. 6). The undersides of the stacker arm 33 are each welded to brackets 34, and the brackets 34 are welded to the upper side of a trans verse box section tube 35 so as to form a unified assem-.'

bly. At each end, the box section tube 35 has a drive plate 36 dependent tehrefrom.

The drive transmission to the plate 36 on each side of the conveyor is identical, one side being a mirror image of the other. For convenience and simplicity however, only one side of the assembly is shown in the drawings and described hereinafter.

An outwardly facing channel guide 37 is mounted in the frame 28 immediately inwardly of the drive plate 36. A drive pin 36a extends through the drive plate 36 and carries on one end a roller 38 engaging in the channel guide 37. The other end of the pin 36a has one end of a connecting link 39 journalled thereon.

. A main drive shaft 40.is journalled transversely in the frame 28 at a position towards the front end of the conveyor and is driven by drive means (not shown) located at a central position. The drive means may be of any conventional kind such as an electric motor or a belt drive. At each end, the drive shaft 40 is overhung and constitutes the main shaft of a compound crank mechanism generally indicated at 41 in FIG. 6. As mentioned above, only one crank mechanism will be described as both are functionally identical.

The compound crank mechanism 41 comprises a primary crank 42 keyed to the end of the shaft 40 and having a rotatable crank pin 43 extending axially through its extremity. One ene of the crank pin 43 has one end of a secondary crank 44 keyed thereon. The other end of the crank pin 43 has a sprocket wheel 45 keyed thereon. A further sprocket wheel 46 is secured to the frame 28 coaxially'with the shaft 40 and in alignment with the sprocket wheel 45, the sprocket wheel 46 having twice as many teeth as the wheel 45. A sprocket chain 47 engages around both of the sprocket wheels 45 and 46. The extremity of the secondary crank 44 carries a crank pin 48 on which the other end of the connecting link 39 is journalled. The spacing between the crank pins 43 and 48 is slightly greater than the spacing between the crank pin 43 and the mainshaft 40 so that the crank pin 48 will follow an elongated elliptical path somewhat similar to the path R shown in FIG. 1. It will be appreciated that the positioning of the crank pin 48 along the secondary crank 44 will thus determine the length of stroke effected by the crank mechanism.

In operation, rotation of the shaft 40 by the drive meanscauses rotation of the primary crank 42 in one direction. During this movement, the sprocket and chain arrangement 45, 46 and 47 causes counter rotation of the crank pin 43 such that the crank pin and the secondary crank 44 perform a single revolution for each single revolution of the primary crank 42. The crank pin 48 is thus constrained to follow the elliptical path above-mentioned and this movement is transmitted to the connecting link 39.

In consequence, the drive plates 36 at each end of the box section tube 35 are subjected to a reciprocal motion through the drive pins 36a. This movement is in turn transmitted to the stacker arms 33 and has an amplitude corresponding to the length of the major axis of the eliiptical path followed by the crank pin 48. During the longitudinal movement of the arms 33, they are subjected to a slight lifting action at their forward ends for a purpose not encompassed by the present invention. This movement is permitted by a rocking action of the tube 35 and plates 36 about the fulcrum formed by the drive pin 36a.

FIG. 8 shows the relationship between the various parts of the compound crank mechanism during different stages of a cycle.

We claim:

1. A mechanism for converting rotarymotion into reciprocating motion, comprising support means,

a drive shaft mounted for rotation in the support means and adapted to be connected to drive means,

a primary crank fixed at one end to the shaft and radiating therefrom to rotate therewith,

a first sprocket wheel adjacent the primary crank and fixed against rotation, the axis of rotation of said first wheel being axially aligned with the longitudinal axis of the drive shaft,

a first crank pin journalled in the primary crank spaced from and parallel with the drive shaft,

a second sprocket wheel fixed to ,the first crank pin in the same plane as the first sprocket wheel, said second wheel being smaller than the first wheel,

a sprocket chain trained around said sprockets,

a secondary crank fixed at one end to said first crank pin and extending back generally in the direction of the drive shaft,

a second crank pin carried by the secondary crank spaced from the first pin and substantially in a first plane including the drive shaft,

a connecting link connected at one end to the second crank pin, and

means constraining an opposite end of the connecting link to move in a second plane substantially parallel with said first plane.

2. A mechanismas claimed in claim 1 in which said first sprocket wheel has a diametertwice that of said second sprocket wheel.

3. A mechanism as claimed in claim 1 in which the length of said secondary crank is greater than the radius of the second sprocket wheel.

4. A mechanism as claimed in claim 3 in which the first sprocket wheel has twice as many teeth as the second sprocket wheel.

5. A mechanism as claimed in claim 1 in which the spacing between the first crank pin and the second crank pin is greater than the spacing between the first crank pin and the drive shaft. 

1. A mechanism for converting rotary motion into reciprocating motion, comprising support means, a drive shaft mounted for rotation in the support means and adapted to be connected to drive means, a primary crank fixed at one end to the shaft and radiating therefrom to rotate therewith, a first sprocket wheel adjacent the primary crank and fixed against rotation, the axis of rotation of said first wheel being axially aligned with the longitudinal axis of the drive shaft, a first crank pin journalled in the primary crank spaced from and parallel with the drive shaft, a second sprocket wheel fixed to the first crank pin in the same plane as the first sprocket wheel, said second wheel being smaller than the first wheel, a sprocket chain trained around said sprockets, a secondary crank fixed at one end to said first crank pin and extending back generally in the direction of the drive shaft, a second crank pin carried by the secondary crank spaced from the first pin and substantially in a first plane including the drive shaft, a connecting link connected at one end to the second crank pin, and means constraining an opposite end of the connecting link to move in a second plane substantially parallel with said first plane.
 2. A mechanism as claimed in claim 1 in which said first sprocket wheel has a diameter twice that of said second sprocket wheel.
 3. A mechanism as claimed in claim 1 in which the length of said secondary crank is greater than the radius of the second sprocket wheel.
 4. A mechanism as claimed in claim 3 in which the first sprocket wheel has twice as many teeth as the second sprocket wheel.
 5. A mechanism as claimed in claim 1 in which the spacing between the first crank pin and the second crank pin is greater than the spacing between the first crank pin and the drive shaft. 